A combine harvester is a machine that is used to harvest grain crops. The objective is to complete several processes, which traditionally were distinct, in one pass of the machine over a particular part of the field. Among the crops that may be harvested with a combine are wheat, oats, rye, barley, corn, soybeans, flax or linseed, and others. The waste (e.g. straw) discharged on the field includes the remaining dried stems and leaves of the crop which may be, for example, chopped and spread on the field as residue or baled for feed and bedding for livestock.
A combine harvester cuts crop using a wide cutting header. The cut crop may be picked up and fed into the threshing and separating mechanism of the combine, typically consisting of a rotating threshing rotor or cylinder to which grooved steel bars commonly referred to as rasp bars or threshing elements may be bolted. These rasp bars thresh and aid in separating the grains from the chaff and straw through the action of the drum against the concaves, i.e., shaped “half drum,” that may also be fitted with steel bars and a meshed grill, through which grain, chaff and smaller debris may fall, whereas the straw, being too big or long, is carried through to the outlet. The chaff, straw, and other undesired material are returned to the field via a spreader mechanism.
In an axial flow combine, this threshing and separating system serves a primary separation function. The harvested crop is threshed and separated as it is conveyed between a longitudinally arranged rotor and the inner surface of an associated chamber comprising threshing and separating concaves, and a rotor cage or cover. The cut crop material spirals and is conveyed along a helical path along the inner surface of the chamber until substantially only larger residue remains. When the residue reaches the end of the threshing drum, it is expelled out of the rear of the combine. At the same time that MOG is being expelled from the combine, the grain, chaff, and other small debris fall through the concaves and grates onto a cleaning device or shoe. For ease of reference, this smaller particulate crop material that contains the grain and chaff is referred to as threshed crop. The grain still needs to be further separated from the chaff by way of a winnowing process.
Clean grain is separated out of the threshed crop by way of a flat oscillating cleaning system that can include a combination of oscillating screens (sieves), a fan which blows air through/above/beneath the sieves, and some mechanism which transports the crop material to be cleaned from beneath the threshing system to the sieves. Clean grain that is separated from the residue via the sieves is typically transported to a grain tank in the combine for temporary storage. The grain tank is typically located atop the combine and loaded via a conveyer that carries clean grain collected in the cleaning system to the grain tank. The grain may then be unloaded through a conveying system to a support trailer or vehicle, allowing large quantities of grain to be unloaded in the field without needing to stop harvesting when the grain tank fills. During operation, the crop material may be unevenly distributed in the cleaning system (e.g., on one or more sieves) caused by a change in inclination (e.g., harvesting on uneven terrain). Conventional combines may be equipped with uneven distribution compensation mechanisms. During flat ground operation, the cleaning system of a combine moves in 2-dimensional motion, shaking fore/aft with some vertical component. U.S. Pat. No. 7,322,882, which is incorporated herein for its teachings on cleaning system compensation mechanisms, describes a grain cleaning side-shaking mechanism which provides compensation to the cleaning system when the combine experiences a change in inclination (i.e. harvesting on uneven terrain). Other side-shaking mechanisms are described in U.S. Pat. No. 4,736,753; U.S. Pat. No. 7,927,199; and U.S. Pat. No. 7,322,882, which are also incorporated herein for their teachings on cleaning system compensation mechanisms. Conventional side-shaking mechanisms, do not affect any changes to the 2-dimensional (fore/aft/vertical) movement of the cleaning system on flat ground. On inclined ground, however, the side-shaking mechanisms introduce an additional side-to-side component in the shake geometry of a sieve, causing material to resist its natural tendency to migrate to the lower side of the sieve and remain more evenly distributed across the width of the sieve, providing a more efficient cleaning system.
Crop material may also be distributed unevenly in the cleaning system during flat ground operation. Accordingly, an improved system is needed to more evenly distribute the crop material across the width of the sieve during flat ground operation. Further to this, the controls of conventional side-shake system operating levels are based on algorithms relating directly to the inclination of terrain. The controlling logic for the side-shake compensation may not always result in evenly distributed grain across the width of the cleaning system due to a number of factors incremental to ground inclination.